This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. NikR is a key regulatory transcription factor for pathogenic microorganisms that depend on nickel enzymes such as urease and NiFe-hydrogenase for survival. Without a proper amount of Ni2+ these bacteria are unable to survive in certain conditions, such as low pH or anaerobic environments. However, an excess of Ni2+ in the cell can cause apoptosis, thus regulating the concentration of Ni2+ in the cell is of great importance. For these reasons we study the bacterial Ni2+-regulatory transcription factor, NikR. To date, we have published a number of structures of Escherichia coli NikR (EcNikR) that have helped elucidate the overall structure of NikR, the metal binding processes, and NikR-DNA binding mechanism. These structures include: the full-length apo-EcNikR and the Ni2+-bound regulatory domain (Schreiter et al., Nature Structural Biology 10 (2003), 794), full-length nickel-activated EcNikR and the EcNikR-operator DNA complex (Schreiter, et al., PNAS 103 (2006), 13676), and apo, Cu2+-, and Zn2+-bound metal binding domain (MBD) of EcNikR (Phillips, et al., Biochemistry 47 (2008), 1938).